The present invention relates generally to multiple beam communication systems and more particularly, to a method and apparatus for digitally controlling a received signal that is manipulated by a digital beam former.
Current commercial high altitude communication devices having conventional multiple beam architectures, which use multipatch antennas, incorporate digital beam forming (DBF) techniques. Multipatch antennas receive and convert communication signals into received signals. Multipatch antennas are also very useful in forming multiple simultaneous beams covering a large field of view (FOV).
Now referring to FIG. 1, a block diagrammatic view of a receiving circuit 10 of a conventional high altitude communication device is shown. Typical mobile satellite payloads have a multipatch antenna 12. The multipatch antenna 12 includes a plurality of patches 14, each patch 14 receives communication signals 16. Each patch 14 is preferably used only once in receiving communication signals 16 to prevent signal to noise degradation.
The configurations of the patches 14 affect the optimization of multipatch antenna axial ratio (AR). Typical multipatch antennas usually have a poor AR. With a good design, 2 db AR over a large FOV is commonly accepted. For limited FOV applications such as a geosynchronous orbit satellite, grouping patches 14 with proper orientation significantly improves the AR to 0.2 db or less.
Orientations of the patches 14 also affect the amount of created grating lobes. The patches 14 have element patterns. When element patterns overlap grating lobes are created. Grating lobes reduce multipatch antenna directivity and gain as known in the art.
The patches 14 are combined in even numbered groups by combining networks 18 to form array elements 19. The combining networks 18 convert the communications signals 16 into combined signals 20. Each combining network 18 is connected to several components for signal-conditioning the combined signals 20 prior to connecting to a digital beam former 22. The combining networks 18 are connected to a plurality of low noise amplifiers (LNAs) 24, which amplify the combined signals 20 to form received signals 26. The LNAs 24 are connected to a plurality of downconverters 28. The downconverters 28 convert the high frequency received signals 26 to baseband or intermediate frequency (IF) signals 30. The baseband signals 30 are then transformed into digital signals 32 by analog-to-digital (A/D) converters 34.
Now referring to FIG. 2, a schematic view of sample array element 19 and a combining network 18, which together optimize axial ratio and prevent grating lobes is shown. The communication signals 16 are received by patches 14 and combined by 3 db hybrids 36 and circular ring hybrids 38 to form the combined signals 20. The patches 14 are oriented 90xc2x0 in sequence. The 3 db hybrids 36 are at 90xc2x0 and the circular ring hybrids 38 are at 180xc2x0. The 3db hybrids 36 and the circular ring hybrids 38 cause signal losses due to their internal characteristics.
Now referring to FIG. 3, a block diagrammatic view of the multipatch antenna 12 showing the positioning of the array elements 19 is shown. The patches 14 are positioned to minimize overlapping of element patterns, thereby, suppressing grating lobes and maximizing gain. By orienting the patches 14 and array elements 19 so that spacing between patches 14 is approximately equal to half the wavelength of the received signal 26 and spacing between array elements 19 is approximately equal to the wavelength of the received signal 26, grating lobes can be prevented.
In high altitude communication devices there is a continuing effort to decrease the amount of components in the system thereby decreasing the size and weight of the system, decreasing hardware, decreasing costs, decreasing power consumption, and increasing efficiency.
In space systems, where up to thousands of array elements may be used, a reduction in satellite payload components may cause tremendous savings. In other communication systems, in which many array elements are used the savings in cost, weight, and power will also be increased.
Therefore a need exists to reduce the number of components in the high altitude communication device. Also a need exists to produce a high altitude communication device having zero grating lobes, good axial ratio, and a reduced amount of signal loss over existing high altitude communication device.
The forgoing and other advantages are provided by a method and apparatus of digitally controlling a received signal within a high altitude communication device. The high altitude communication device uses a first array element comprising a plurality of patches and a second array element comprising a plurality of patches. The first array element and the second array element are for receiving communication signals. A patch in the first array element is shared by the second array element.
A method of digitally controlling received signals within a high altitude communication device is provided. The method includes clocking an array element and receiving communication signals. The communication signals are converted to digital baseband signals by the plurality of grouping networks. The plurality of grouping networks also transforms the digital baseband signals into digital combined signals.
The present invention has several advantages over existing signal controlling techniques. One advantage of the present invention is that it reduces the number of high altitude communication device components by eliminating the use of hybrids and combining networks. The reduction in components reduces weight and saves space within a high altitude communication device. Furthermore, the reduction in components reduces costs involved in production and implementation of satellite systems.
Another advantage of the present invention is that it minimizes signal losses due to the elimination of the hybrids and combining networks.
Yet another advantage of the present invention is that an arbitrary number of patches may be grouped together as opposed to a fixed hardwired even amount of patches.
Moreover, the present invention eliminates grating lobes and optimizes the high altitude communication device axial ratio. The present invention also reduces A/D dynamic range requirements and may be easily calibrated and recalibrated.
Therefore, a high altitude communication device having a minimal number of components, which can digitally control received signals, is possible due to the stated method advantages. The present invention itself, together with further objects and attendant advantages, will be best understood by reference to the following detailed description, taken in conjunction with the accompanying drawing.
For a more complete understanding of this invention reference should now be had to the embodiments illustrated in greater detail in the accompanying figures and described below by way of example.
In the figures:
FIG. 1 is a block diagrammatic view of a receiving circuit of a conventional high altitude communication device.
FIG. 2 is a schematic view of an array element in conjunction with a combining network of a conventional high altitude communication device.
FIG. 3 is a block diagrammatic view of a multipatch antenna of a conventional high altitude communication device showing positioning of array elements.
FIG. 4 is a perspective view of a communication system, utilizing a method and apparatus for sampling communication signals according to the present invention.
FIG. 5 is a block diagrammatic view of a high altitude communication device in accordance with the present invention.
FIG. 6 is a block diagrammatic view of a receiving circuit of a high altitude communication device in accordance with the present invention.
FIG. 7 is a block diagrammatic view of a multipatch antenna of a mobile satellite payload in accordance with the present invention.
FIG. 8 is a block diagrammatic view of clocking groups of patches in accordance with the present invention.
FIG. 9 is a flow chart illustrating a method of digitally controlling received signals within a high altitude communication device according to the present invention.